Enzymatic crosslinking is the way in which our blood clots during wound healing – cells secrete an enzyme, transglutaminase, which crosslinks fibrin, forming an insoluble protein polymer, or clot. By using this enzyme, along with the appropriate functional groups, hydrogels can be crosslinked in much the same way.

Although it’s instantly recognized from the food industry, gelatine is used in a wide variety of applications – from photography to food to pharmaceuticals to tissue engineering & regenerative medicine.

Some of the earliest hydrogels used for cell encapsulation were, (not ironically) naturally derived, ionically crosslinked materials, such as alginate, chitin and agarose. Although somewhat low-tech, these were a natural place to start.

Most people are familiar with Jell-O or jelly desserts – probably the most widely used and well known hydrogel ever used. Jell-O is made by dissolving gelatin, a protein polymer produced from collagen, in warm water.